Genome-wide association mapping reveals loci for enzymatic discoloration on cut lettuce

Authors: PENG, HUI - University Of Florida; Luo, Yaguang - Sunny; TENG, ZI - University Of Maryland; Zhou, Bin; Pearlstein, Daniel; WANG, DONGYI - University Of Arkansas; Turner, Ellen; Nou, Xiangwu; Wang, Thomas - Tom; TAO, YANG - University Of Maryland; Fonseca, Jorge; Simko, Ivan

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2023
Publication Date: 9/27/2023
Citation: Peng, H., Luo, Y., Teng, Z., Zhou, B., Pearlstein, D.J., Wang, D., Turner, E.R., Nou, X., Wang, T.T., Tao, Y., Fonseca, J.M., Simko, I. 2024. Genome-wide association mapping reveals loci for enzymatic discoloration on cut lettuce. Postharvest Biology and Technology. 207. Article 112577. https://doi.org/10.1016/j.postharvbio.2023.112577.
DOI: https://doi.org/10.1016/j.postharvbio.2023.112577

Interpretive Summary: Lettuce is one of the most popular leafy vegetables in the world. Total farm gate value of lettuce has exceeded $2.7 billion in U.S. in recent years. Lettuce plants are usually processed as the major components of ‘ready-to-eat’ salad products or sold as whole heads. Both products rapidly develop oxidative discoloration (a combination of tissue browning and pinking) on the cut surface when being packed in aerobic conditions, severely reducing their market acceptance and thus leading to substantial economic losses. The discoloration did not show association with plant developmental rate, yellow spot malady, bacteria leaf spot, or downy mildew but displayed a significant association with the initial levels of brownness and greenness in ribs, and the deterioration rate of fresh-cut lettuce packaged in modified atmosphere. The trait exhibited a relatively high broad-sense heritability in four experiments conducted at three locations in three years and performed with 374 accessions representing diverse lettuce types. We have detected six loci significantly associated with the oxidative discoloration and identified candidate genes involved in regulating the rate of postharvest discoloration.

Technical Abstract: Lettuce is prone to oxidative discoloration during postharvest storage, leading to food waste and economic loss. Identifying the genetic determinants and physiological factors influencing postharvest discoloration can help facilitate its control. The discoloration did not show association with plant developmental rate, yellow spot malady, bacteria leaf spot, or downy mildew but displayed a significant association with the initial levels of brownness (r = -0.146, p < 0.05) and greenness (r = -0.255, p < 0.001) in ribs, and the deterioration rate (r = 0.391, p < 0.001) of fresh-cut lettuce packaged in modified atmosphere. The trait exhibited a relatively high broad-sense heritability (H2 = 0.669) in four experiments conducted at three locations in three years and performed with 374 accessions representing diverse lettuce types. The genome-wide association study (GWAS) revealed the significant effect of six loci (qDis1.1, qDis4.1, qDis6.1, qDis8.1, qDis8.2, and qDis9.1) defined by eight SNP markers. A total of 965 genes were predicted in the identified chromosomal regions, with three quinone oxidation-reduction catalyzers and 19 transcription factors being potentially the most promising candidate genes involved in regulating the rate of postharvest discoloration.